Two eating disorders, binge eating disorder (BED) and the night eating syndrome (NES), have been associated with obesity. There is reason to believe that they contribute to the obesity and that controlling them might contribute to the control of obesity. The prevalence of these disorders is not known. We hope that this proposed study will help to determine this prevalence and the extent to which the disorders are associated with the severity of obesity. Binge eating disorder is characterized by a subjective feeling of loss of control over what is being consumed and an objective consumption of an amount of food "definitely larger than most people would eat." Night eating syndrome consists of morning anorexia, evening hyperphagia, lowering of mood late in the day, and nighttime awakenings, during which time food-usually high in carbohydrates is consumed. Our proposed study seeks to delineate how common each of these eating disorders is among the Look AHEAD population and, if possible, the stability of the diagnosis in the course of the first year of treatment. One thousand randomly selected subjects from five Look AHEAD sites, including both men and women and irrespective of race or ethnicity, will be administered screening questionnaires that assess both the BED and NES criteria. From those screening questionnaires, 20 percent of persons with the highest scores for NES and those scoring above a cutoff (20 percent +/-5 percent) for BED will be contacted for follow-up clinical phone interviews to reduce the number of subjects who are falsely self-identified. This information will be gathered upon subjects' entry into the Look AHEAD trial and again at six months and one year into treatment to assess the stability of the diagnosis.